Tunnel kiln



P. A. MEEHAN TUNNEL KILN Oct. 18 1927.

, 2 Sheets-Sheet 1,

INVENTOR- PAUZ /4.M//A/V M M g /ATTORNEY Filed July '7. 1926 Patented Oct. 18, 1927.

UNITED STATES 1,546,208 PATENT OFFICE.

PAUL A. MEEHAN, OF CLEVELAND, OHIO, ALSSIGNOR TO AMERICAN DRESSLER TUNNEL KILNS, INC., 0F CLEVELAND, OHIO, A CORPORATION OF NEW YORK.

TUNNEL KILN.

Application filed July 7, 1926. Serial No. 120,903.

The general object of my present invention is to prov ide an improved circulation system for tunnel kilns. More specifical y, t e object of the present invention is to provide simple and effective means for maintaining a forced circulation of the atmoshere of a kiln by the inipelling action of ets of heated air or gas forced into the kiln chamber. The invention is especially applicable to tunnel kilns of either the mufile or direct re type, but mayalso be used with periodic -own-draft and other types of intermittent kilns.

These and other features of novelty which characterize my invention are pointed out with particularity in the claims annexed to and forming a part of this specification. For a better understanding of the invention, however, its advantages and specific objects attained with its use, reference should be had to the accompanying drawings and descriptive matter in which I have illustrated and described preferred embodiments of this invention.

In the drawings:

Fig. 1 is a side view of a portion of a tunnel kiln including the entrance section and preheating zone;

Fig. 2 is a section of the muilie kiln on the line 2-2 of Fig. 1;

Fig. 3 is a sect-ion showing my invention applied to a kiln of the direct fired type;

Fig. 4 is a section of a direct fired kiln showing a modified form of my invention; and i Fig. 5 is a modified form of the last injector.

In the drawings, a tunnel kiln A is shown having a kiln chamber through which move the cars B carrying ware C which is to be heat treated. Longitudinally spaced along the top of the preheating zone of the tunnel kiln are openings to the kiln chamter crown and in these openings are arranged the injecting means. My invention is of especial value in connection with the preheating zone of the kiln. However, the principle and application can be used wherever a forced circulation is desirable.

In the mufiie kiln chamber, as shown in Fig. 2, with the combustion chambers D located'along the side walls and the ware car on tracks along the middle portion of the kiln, the natural convection circulation of the kiln atmosphere is upwardly from the combustion chambers D to the kiln crown, downwardly "through the ware stacks along the center line of the kiln and through the refractory body passages to the sides of the kiln chamber. The impelling jets of the present invention are designed to increase the atmospheric circulation along the paths of the natural convection circulation.

Arranged in each of the openings in the top of the kiln chamber is an impelling jet apparatus consisting of a hollow casting G supported on the kiln crown by the flanges G and serving as a support for a series of in ecting and mlxing nozzles K K and K through which passes the impelling jet from anozzle K. p The injecting nozzles K K and K supported by brackets (it and G on an inner flange G of the hollow casting, consists of three downwardly taperin elements with circular inlets and outlets 3f increasing diameters, and the outlet of each ot the upper nozzles extending slightly into the inlet of the next lower nozzle. On top of the casting G is positioned a removable cover plate G and through the center of which pro ects a pipe F having the nozzle l\ secured to the end thereof. The lowermost nozzle K is shown with a circular discharge portion. A modified form of this discharge outlet is shown in Fig. 5 as being fan shaped with a rectangular base, the greater dimension of the base eXtendin" parallel to thedongitudinal center line 0? the kiln.

The car B is arranged with the Ware C stacked on both sides of the car leaving a vertical passageway (1 down through the middle of the ware. 1n the refractory bodies forming part of the \vure supporting means of the car are located circulation passages C opening to the passage C and to the sides of the kiln chamber at the bench level of the kiln. In the side walls of the kiln chamber are positioned pipes H opening to the atmosphere and to the kiln chamber. The pipes H arcshown with removable plugs in the outer openings, the plugs being removed when an outlet to the atmosphere is necessary. Connecting pipes H for the spaced pipe openings H are shown in Fig. 1. Arranged in the kiln chamber walls are the pipes H and H connecting the pipes H to the mixing chamber at the kiln crown. Passages H, Hiand H are formed about the oottom and sides, respectively, of the comr especiall 'and is connected to oneof thepipes F.

The valve's F are 'used to control the supply of hot gases to the pipesFland are useful when an injector is to be inspecte or removed for repairs.

The circulation of the kiln atmosphere follows the paths shown by the arrows.

The hot gases from the main E under pres-' sure are ejected from the nozzle K into the mixing chamber G where stages K and K draw on the atmosphere at the kiln crown.

The resulting mixture of hot gases and kiln atmosphere flows under pressure through the last stage of the injector K which exerts an impelling action on the atmosphere at the top of the kiln chamber. The stream of' mixed gases which flows downwardly in the passage G between the ware stacks, is divided into separate streams b the passages C Part of each stream ows to the kiln crown through the pipesH, H and H where it enters the mixing chamber G. The remaining portion flows upwards through the passages H and H to thetop of the kiln chamber where it mixes with the impelling jet in the nozzle K. It is apparent that the forced circulation of the kiln atmosphere follows the natural convection circulation paths of flow which is very desirable. The longitudinal flow of the kiln atmosphere is restricted by baffles A in the usual manner,

The impelling jets can be introduced into the kiln chamber at various points depending upon the type of kiln in which it is to be installed and the desired circulation of the I kiln chamber atmosphere. 'In Fi s. 3 and 4 are shown two modified forms 0 the injection system applied to direct fired kilns. Thecirculation of the kiln atmosphere is shown by the arrows. the injection gases may be taken from the kiln itself or from the exhaust fan.

The former constructions where a forced circulation of the kiln atmosphere was desirable, a multiplicity of fans atvarious points along the kiln were necessary. Great difiiculty and expense were incurred by the deteriorating action of the hot gases on the propelling mechanism. In the present invention, a single fan (not shown) is sufficient to force the hot gases from the, recuperator or some other suitable source such as kiln cooling zone under suflicient pressure to distribute the gases to the spaced nozzles.

In cases where outside air is introduced In a direct fired kiln into the kiln in this way, the excess added to the kiln atmosphere will be exhausted by a fan located in the entrance end of the kiln to control the longitudinal flow of the kiln atmosphere.

While in accordance with the provisions ofthe statutes, I have illustrated and described the best forms of my invention now knownto me, it will be apparent to those skilled in the art that changes may be made in the forms of the apparatus disclosed Without departing from the spirit of my invention, as set forth in the appended claims and that certain features of my invention may sometimes be used to advantage without a corresponding use of other features.

Having now described my invention, what' I claim as new and desire to secure by Letters Patent is:

l..In a kiln, means for circulating the kiln chamber atmosphere comprising a channel in the kiln chamber wall opening to the kiln chamber at separated points and an injector having a mixing chamber adjacent on of said channel openings.

2. In a kiln, means for circulating the kiln atmosphere comprising a channel in the kiln chamber wall opening to the kiln chamber at the bench level and top of the kiln and an injector having a mixing nozzle in one of said openings.

3. In a kiln, means for circulating the kiln atmosphere comprising a channel in the kiln chamber wall opening to the kiln chamber at separated points and an injector consisting of a series of mixing nozzles located in one ofsaid channel openings.

4. In a kiln, means for circulating the kiln atmosphere comprising a channel in the side wall of the kiln chamber opening to the chamber at separated points and an injector comprising an injection nozzle and a series of superposed mixing nozzles located in one. of said openings.

. 5. In a circulation system for a tunnel kiln, the combination with a ware supporting kiln car, of a superposed series of injecting nozzles located in the kiln crown, circulation passages through the side walls of the kiln and the body of said car, and means for passing hot gases under pressure through said nozzles to establish a force circulation system through said were car and the side the nozzle jets to establish a forced circulation of the kiln atmosphere.

8. In a tunnel kiln, an injector for accelerating the kiln atmosphere circulation comprising a superposed series of downwardly tapering nozzles supported in an opening in the kiln crown, the inlet and. discharge openings of said nozzles being of increasing area.

9. In a continuous tunnel kiln, a circulation' injector system comprising a series of superposed nozzles forming a multi-stage injector, several stages of which draw on the kiln atmosphere and a stage drawing on the 1 external atmosphere.

10. In a continuous tunnel kiln, a series of injecting nozzles located in the preheating zone portion of the kiln chamber, means for passing heated ases into the kiln cham her through each 0% said nozzles, and circulation passages formed in the walls of said kiln chamber and each opening to the latter at spaced points, one of which is adjacent a corresponding injecting nozzle, whereby the jets discharged by said nozzles set up a circulation of the kiln atmosphere.

11. In a tunnel kiln, the combination with an injector nozzle in the kiln chamber, of a kiln car carrying ware to be heat treated through the kiln chamber, said car being PA UL A. MEEHAN. 

